Electromagnetic clutch



Nov.,25, 1969 9.1... alLLlNes ET 3,430,124

I I ELECTROMAGNETIC CLUTCH Filed April 22, 1968 FWQZ INVENTORS DAVID L.BILLINGS &ROBERT M. F'EY WW/ 5m THUR ATTORNEY United States Patent O MUS. Cl. 19284 6 Claims ABSTRACT OF THE DISCLOSURE In a clutch of thetype including an electrical coil for inducing a magnetic field betweenthe relatively movable clutch structures to operatively interconnectthem; one of the structures defines an annular cavity to receive thecoil and the coil is wound on a bobbin of electrically insulativematerial which is then received in the cavity. The bobbin includes anumber of spaced bosses which are received in complementary holesprovided in the clutch structure and two oppositely positioned ones ofthe bobbins serve as mountings for the coil terminals. An annular stripof electrically insulative material is provided with a pair of spacedslip rings and includes an equal number of spaced openings with eachopening communieating with a different one of the slip rings than theopening disposed opposite it. The strip is mounted on the clutchstructure by means of conductive connectors, such as screws, whichextend through the openings and holes. Each one of an oppositelydisposed pair of the screws engage a slip ring and a terminal. Thus thebobbin and the annular strip are securely mounted on the clutch whilethe slip rings are electrically connected to the coil.

BACKGROUND OF THE INVENTION This invention relates to clutches and, moreparticularly, to electromagnetic clutches. In such devices a rotaryinput and a rotary output structure are mounted in juxtaposition and acoil is mounted on one of them to induce a magnetic field in them andthus operatively interconnect them. Normally the coil is mounted withinthe clutch and slip rings must be mounted on an exterior surface of theclutch to electrically connect the coil to a control which is mounted onsome stationary portion of the ma chine involved. Providing securemechanical connection of the coil and slip rings to the clutch structurewhile, at the same time, electrically interconnecting these elements hasposed substantial problems in the prior art.

An object of this invention is to provide an improved electromagneticclutch.

Another object is to provide such a clutch having an improvedarrangement for mechanically mounting the coil and slip rings and, atthe same time, providing electrical connections therebetween.

A further object of this invention is to provide such an improved clutchwherein the mounting and electrical connection is provided with aminimum number of long lasting, low cost parts.

A still further object of this invention is to provide such an improvedclutch wherein any possible problem of proper orientation between thecoil and slip rings during assembly is eliminated.

SUMMARY OF THE INVENTION An electromagnetic clutch is provided with arotary input structure and an adjacent, rotary output structure. One ofthese structure defines an annular cavity therein to receive anelectrical coil for inducing a magnetic field in the input and outputstructures to operatively interconnect them and defines a plurality ofspaced holes therethrough communicating with the cavity. An annular bob-3,480,124 Patented Nov. 25, 1969 ice bin or coil support means ofinsulative material, having an electrical coil wound thereon, isreceived in the cavity and includes a plurality of spaced bosses whichare received in the holes. A pair of the bosses provide mounting for apair of terminals connected to the ends of the coils. An annular stripof insulating material is provided having a pair of spaced slip rings ofconductive material formed thereon. The strip and slip rings define apair of spaced openings with each one of the openings communicating witha different one of the slip rings. The strip is .placed in juxtapositionto the clutch structure with separate conductive securing means engagingone of the slip rings, extending through aligned ones of the holes andopenings and engaging one of the terminals so that the bobbin and stripare securely mounted on the clutch structure and the slip rings and coilare electrically connected.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a side elevational view ofa clutch made in accordance with one form of the present invention, themechanism being shown partially broken away and partially in section toillustrate details;

FIGURE 2 is a perspective view of a portion of the input structure ofthe clutch of FIGURE 1, the view being partially broken away andpartially in section to illustrate details;

FIGURE 3 is a reduced scale plan view of the strip of insulativematerial used in the clutch of FIGURE 1, illustrating the slip rings andthe openings therethrough; and

FIGURE 4 is a view taken along line 44 of FIGURE 1, illustrating certaindetails of the clutch mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawingthere is shown an electromagnetic clutch 1 including a rotary inputstructure 2 and an adjacent rotary output structure 3. The inputstructure is provided with a first or inner, generally radiallyextending wall 4 which is mounted on the shaft 5 of a suitable motor 6for rotation therewith by any suitable arrangement such as the key andslot generally illustarted at 7. The outer periphery of the wall 4 joinsone edge of an inner, axially extending wall 8. Adjacent its outer edge,the wall 8 joins a second, or outer, radially extending wall 9. Theouter periphery of the wall 9 joins an outer axially extending wall 10,which is radially spaced from and parallel to the wall 8, so that thewalls 8', 9 and 10 in effect form a recess or cavity in the input structure. The edge of the wall 10 is formed as a clutching surface 11.

The output structure 3 can be connected to drive any suitable mechanismand, for purposes of illustration, it is shown as including an outputpulley or hub 12 mounted on the motor shaft 5 by means of a bearingstructure 13 so that it can rotate relative to the shaft. The outputstructure also includes an outer, annular clutching member 14 which ismounted in juxtaposition to the clutching surface 11 of the inputstructure and is connected to the pulley 12 by an intermediate member15. The intermediate member 15 is connected to the pulley 12 and theclutching member 14 by any suitable means such as rivets indicated at16. The clutching member 14 is provided with an annular strip offriction material 17 for engagement with the clutching surface 11.

In order to provide mutual attraction between the input and outputstructures so that the clutching surface 11 and strip of frictionmaterial 17 are brought together with sufiicient force to operativelyconnect these structures, an electrical energizing coil is mounted inthe cavity 18 formed by the walls 8, 9 and 10. To this end there isprovided an annular coil support means 19 of electricallyparticularly,'the coil "support means includes an annular,"'

axially extending wall 21 joined to a pair of spaced, radially extendingwalls 22 and 23 to provide a bobbin of Ushaped cross section. The bobbinis open in the radially outward direction, which enables the coil 20 tobe wound thereon easily. A covering 20a of suitable material may bewound around the coil and tied to prevent any slippage of the coil. Thebobbin is received in the cavity 18 with its axially extending wall 21mounted closely around the wall 8 of the input structure. v

The radial wall 23 is formed with a plurality of hollow bosses 24 asshown in FIGURE 1 and 25 shown in FIG- URE 3 which are spaced around thecircumference of the wall. These bosses 24 and 25 are received in holes26 formed in the wall 9 of the input structure so that the wall 23 ofthe bobbin will fit flush with the inner surface of the wall 9. Whilethe bosses may all be formed to be symmetric in configuration, for easeof manufacturing the bosses 24 are formed to open radially outward whilethe bosses 25 open tangentially of the edge of the wall 23. In theclutch illustrated there are a pair of bosses 24 on circumferentiallyopposite sides of the bobbin 19 and each of these bosses receives andmounts a terminal 27 which, in turn, is connected to one end of the coil20. The terminals 27 include a return bent portion 28, which is mountedwithin the bosses 24, and an arm portion 29 which extends from thebosses toward the coil for connection to an end of the wire forming thecoil. Thus the terminals 27 are firmly mounted in the bobbin and at thesame time are electrically insulated from the input structure 4. In theclutch illustrated there also is a pair of bosses 25 which are spacedsubstantially directly across the bobbin from each other and equallyspaced with respect to the bosses 24. The bosses 25 receive generallyU-shaped mounting clips 30. The clips 30 are contained substantiallycompletely within the bosses 25 so that they may be used formechanically securing the bobbin and coil in the clutch while, at thesame time, they are electrically isolated and there is no chance that anend of the coil will be connected to them.

When an electrical current is provided to the coil it sets up a magneticfield which flows through both the input and the output structures andcauses mutual attraction therebetween. This mutual attraction causesfirm engagement between the clutching surface 11 and the frictionmaterial 17 so that the input and output structures are operativelyconnected. To this end there is provided an annular strip ofelectrically insulative material 31 which has formed thereon a pair ofannular, radially spaced, electrically conductive slip rings 32 and 33.Thus the Slip rings are electrically isolated from each other. There isformed in the strip 31 two openings 34 which are on circumferentiallyopposite sides of the strip and one of these openings 34 extends througha portion of the slip ring 32 while the other extends through a portionof the slip ring 33. There are two additional openings 35 formed in thestrip 31 directly opposite from each other and displaced 90 with respectto the openings 34. One of the openings also extends through the slipring 32 while the other extends through the slip ring 33. This formsfour openings through the slip rings and strip which are equally spacedcircumferentially around the strip with one adjacent pair of theopenings extending through or communicating with the slip ring 32 andthe other pair extending through or communicating with the slip ring 33.The openings 34 and 35 are radially spaced so that when the strip 31 ispositioned against the outside of wall 9 the openings 34 and 35 will bein registry with the holes 26 in the wall 9 and with the bosses 24 and25.

In order to assure proper lateral placement of the strip with respect tothe input structure 4, the wall 8 extends beyond the wall 9 to form ashoulder 8a which fits closely within the radially inner edge of thestrip 31, thus fixing the lateral positioning of the strip. All thatthen becomes necessary is to rotate the strip until the openings 34 and35 arealigned withthe openings 26 and thus the bosses 24 and 25'.Conductive securing means such as screws 36 are inserted through theopenings 34 and 35 and holes 26 with the threaded shaft of the screwsextending into the bosses 24 and 25 and being threadedly engaged withthe terminals 27 or clips 30. The heads of the screws overlie and are inengagement with the. slip rings 32 and 33. The alignment of the openings34 and 35 with respect to the holes 26 and the bosses 24 and 25 is of nosignificance. As discussed above the terminals 27 are mounted in thedirectly opposite pair of bosses 25. Also, each of the openings 34communicate with a different one of the slip rings and each of theopenings 35 communicates with a different one of the slip rings. Thus,regardless of the relative positioning of the strip 31 with respect tothe wall 9, each end of the coil 20 will be connected to a different oneof the slip rings 32 and 33.

Electrical power may be provided to the slip rings 32 and 33 through apair of electrically conductive brushes or rods 37. The brushes aremounted in a control housing 38 which is illustrated as being positionedon the motor 6 and disposed under the strip 31. The housing 38 containsvarious control elements forming a control circuit for providing asuitable signal to the slip rings through the brushes. The particularcontrol circuit used forms no part of the present invention and thus aparticular circuit has not been illustrated.

From the foregoing it will be seen that there is provided a new andimproved electromagnetic clutch with a simplified and yet fool proofarrangement for physically mounting the electrical coil and the sliprings on the clutch and, at the same time, electrically interconnectingthe coil and the slip rings with proper isolation of the electricalcircuit from other conductive components of the device.

It will be obvious to one skilled in the art that various modificationsmay be made to thedevice illustrated without departing from the spiritand scope of the invention. For instance, there could be provided onlytwo bosses, spaced directly across the bobbin from each other, two holes26 similarly spaced, and two openings in the insulated strip 31,similarly spaced with one connected to each ofv the slip rings. Wherethe magnetic clutch is to be relatively large it may be desired, forpurposes of the physical mounting of the slip rings and coil to use morethan four screws. By using an even number of connecting devices evenlyspaced circumferentially around the clutch and by making an adjacentone-half of them extend through one slip ring while the other adjacentone-half of them extend through the other slip ring. In which eventthere will be provided a corresponding number of openings, holes andbosses, with the terminals mounted in an oppositely disposed pair of thebosses. With such an arrangement the ease of construction with surety ofproper coil connection may be maintained. The embodiment illustrated isshown with four screws since, in clutches of the type illustrated thatis normally a sufiicient number for mechanical attachment purposes, and,therefore, the number four is an optimum.

What we claim as new and desire to secure by Letters Patent of theUnited States is: r

1. An electromagnetic clutch, including:

(a) a rotary input structure;

(b) an adjacent, rotary output structure;

(c) one of said structures defining an annular cavity therein to receivean electrical coil for inducing a magnetic field in said input andoutput structures to operatively interconnect them;

(d) said one of said structures defining a plurality of spaced holestherethrough communicating with said cavity;

(e) coil support means of insulative material having an electrical coilmounted thereon, said coil support means being received in said cavity;

(f) said coil support means including a plurality of spaced bossesreceived in said holes; a spaced pair of said bosses providing insulatedmountings for a pair of terminals connected to the ends of said coil;

(g) an annular strip of insulating material having a pair of radiallyspaced, slip rings of conductive material formed thereon, said sliprings and said strip having a pair of spaced openings, each one of saidpair of openings communicating with a different one of said slip rings;

(h) said strip being in juxtaposition to said one of said structureswith separate conductive securing means connecting one of said sliprings to one of said terminals and the other of said securing meansconnecting the other of said slip rings to the other of said terminals,said securing means extending through aligned ones of said holes andopenings;

(i) whereby said coil support means and said strip are mounted on saidone of said structures and said slip rings and said coil areelectrically connected.

2. The invention as set forth in claim 1, wherein said coil supportmeans is a bobbin of substantially U-shaped cross-section and has itsopen side disposed in the radially outward direction, whereby said coilmay be easily wound on said bobbin.

3. The invention as set forth in claim 1 wherein there are an evennumber of bosses equally spaced circumferentially around said coilsupport means with a pair of oppositely disposed ones of said bossesproviding the mountings for said terminals; there are an equal number ofholes equally spaced circumferentially around said one of saidstructures; and there are an equal number of openings equally spacedcircumferentially around said strip with an adjacent one-half of saidopenings communicating with one of said slip rings and the otheradjacent one-half of said openings communicating with the other of saidslip rings; whereby each of said terminals will be connected to adifferent slip ring than the other of said terminals regardless of theorientation of said strip relative to said coil support means.

4. An electromagnetic clutch, including:

(a) a rotary input structure;

(b) an adjacent, rotary output structure;

(c) one of said structures including an annular, radially extendingwall, with an inner and an outer, spaced annular wall extending axiallytherefrom; said walls defining an annular cavity to receive anelectrical coil for inducing a magnetic field in said input and outputstructures to operatively interconnect them;

((1) said radially extending wall defining a plurality of spaced holestherethrough communicating with said cavity;

(e) an annular coil support means of insulative material having anelectrical coil mounted thereon, said coil support means being receivedin said cavity;

(if) said coil support means including a plurality of spaced bossesreceived in said holes; a spaced pair of said bosses providing insulatedmountings for a pair of terminals connected to the ends of said coil;

(g) an annular strip of insulating material having a pair of radiallyspaced slip rings of conductive material formed thereon, said slip ringsand said strip having a pair of spaced openings, each one of said pairof openings communicating with a different one of said slip rings;

(h) said strip being in juxtaposition to said radially extending wallwith separate conductive securing means connecting one of said sliprings to one of said terminals and the other securing means connectingthe other of said slip rings to the other of said terminals, saidsecuring means extending through aligned ones of said holes andopenings;

(i) whereby said coil support means and said strip are mounted on saidone of said structures and said slip rings and said coil areelectrically connected.

5. The invention as set forth in claim 4 wherein said coil support meansincludes an annular, axially extending wall joined to a pair of spaced,radially extending walls to provide a bobbin of a generally U-shapedcross-section; said bobbin being received in said cavity with itsaxially extending wall mounted closely around the inner axiallyextending wall of said one of said structures; and one of its radiallyextending walls being formed with said plurality of bosses, which arereceived in said plurality of holes in said radially extending wall ofsaid one of said structures.

6. The invention as set forth in claim 4 wherein there are an evennumber of bosses equally spaced circumferentially around said coilsupport means with a pair of oppositely disposed ones of said bossesproviding the mountings for said terminals; there are an equal number ofholes equally spaced circumferentially around said radially extendingwall of said one of said structures; and there are an equal number ofopenings equally spaced circumferentially around said strip with anadjacent one-half of said openings communicating with one of said sliprings and the other adjacent one-half of said openings communicatingwith the other of said slip rings; whereby each of said terminals willbe connected to difierent slip ring than the other of said terminalsregardless of the orientation of said strip relative to said coilsupport means.

References Cited UNITED STATES PATENTS 2,739,683 3/1956 Gamundi.3,162,285 12/1964 Sala.

CARLTON R. CROYLE, Primary Examiner A. D. HERRMANN, Assistant ExaminerU.S. Cl. X.R. 3l0232

